1. Field of the Invention
The present invention relates to a camera comprising a shutter to cut a reverse-incident light from an eyepiece lens.
2. Description of the Related Art
In recent years, a camera, a so-called electronic camera, which images a subject image on the solid state imaging device (for instance, CCD two-dimensional image sensor) by an imaging optical system to convert it to an electric signal, and then records the obtained image data of the still image on the record medium such as the semiconductor memory and the magnetic disk is spreading widely.
In the electronic camera, a tendency, of which a high function is put in a more compact body, that is, a tendency to so-called miniaturization is strong. And, the result of the miniaturization becomes a large factor to decide the commodity value of the camera.
It is known that an eyepiece shutter is provided to prevent the reverse-incident light from the viewfinder.
However, when the eyepiece shutter is provided near the objective lens, since the diameter of the light flux is large, the large eyepiece shutter is required (see Japanese Patent Application KOKAI Publication No. 3-184028).
The mechanical eyepiece shutter generates dust by the wear etc. at driving. Therefore, the eyepiece shutter is provided at near the focus board in the main body, the dust might adhere to the focus board. Since the dust, which adheres to the focus board is magnified and observed in a view from the viewfinder, unpleasant feeling is given to the user. It is extremely difficult to remove the dust since there is no method to remove the dust except that the camera is decomposed.
In addition, recently, the eyepiece shutter is configured by the liquid crystal element and penetration/non-penetration on the liquid crystal surface is controlled with CPU, which controls the entire camera.
Therefore, the camera enabling the eyepiece shutter to be opened and closed automatically according to appropriate timing is proposed (For instance, see Japanese Patent Application KOKAI Publication No. 11-326985).
However, it is necessary to provide an LED etc. to perform the display in the view of the viewfinder in addition to the liquid crystal element to configure the eyepiece shutter in the viewfinder optical system. Therefore, not only causing the cost up but also miniaturization of the camera is remarkably impaired.
The camera, which prevents the reverse-incident light from the viewfinder by closing the light-shielding board in the viewfinder system, that is, the eyepiece shutter while the shutter in front of each imaging device is opening, is proposed (see Japanese Patent Application KOKAI Publication No. 1-265689). More specifically, after the turning on signal of the release is generated, the eyepiece shutter is closed at once in the camera. Thereafter, the exposure on the imaging device is started by starting run the start curtain of each shutter delaying only during the predetermined time. Then, after the running end of end curtain of each shutter is confirmed, the eyepiece shutter is opened. However, the composition of Japanese Patent Application KOKAI Publication No. 1-265689 is a focal plane shutter of indispensability which has the start curtain and the end curtain. The structure of the focal plane shutter which has the start curtain and the end curtain is complex and downsizing is more difficult than so-called the lens shutters. As a result, it is improper to the miniaturization of the entire camera. Additionally, the focal plane shutter disposed in front of the imaging device usually is closed. Therefore, it is not possible to apply originally to an electronic camera with a type in which the subject image imaged by the imaging device is displayed on the LCD as a through image.
Most of the electronic cameras have the function to execute taking a picture continuously while release button is being pushed, so-called the rapid sequence function.
The following technique is proposed (see Japanese Patent Application KOKAI Publication No. 3-184028). The mechanical switch, which forcibly puts the eyepiece shutter mechanism into an open state, is provided. If the rapid sequence switch is in on state, the eyepiece shutter is kept open with the mechanical switch, and if the rapid sequence switch is in off state, the eyepiece shutter is closed at the time of taking a picture.
Moreover, a technique to control so that the eyepiece shutter is automatically opened in synchronous with the film rolling up operation which is always performed after taking a picture is proposed (see Japanese Patent Application KOKAI Publication No. 54-49136), too.
However, even when the power switch is turned off in a state that the eyepiece shutter is open, it may be happened that the eyepiece shutter changes into a state of close by a shock applied to the camera main body etc. When the eyepiece shutter enters the close state, the photographing operation cannot start immediately when looking in the viewfinder, and a valuable shutter chance is missed even if tries to take a picture and the power supply switch is turned on again.
Moreover, a technique in which the eyepiece shutter of the camera is automatically opened and closed in synchronous with the shutter release, in a word, the photographing operation, which is a main operation of the camera, is also proposed (see Japanese Patent Application KOKAI Publication No. 10-20365).
However, the eyepiece shutter is opened and closed only in synchronous with the shutter release, in a word, the photographing operation which is a main operation of the camera. Therefore, it is not considered in any way in case of the other case such as setup operations of the white balance adjustment function and the exposure adjustment function.
When a control of which the eyepiece shutter is always closed as mentioned above at the release operation is adopted, operativeness lowers because the photographer cannot observe the subject image meanwhile. In addition, the open and close of the eyepiece shutter repeated every time is annoyed on eyes.
Moreover, since a dark output by a so-called dark current etc. exists in the imaging device, the picture quality is degraded because the dark output is superimposed on the image signal.
An electronic camera, which improves the point that it is insufficient to evaluate the defect pixel only before shipping it in the factory, is proposed, since the pixel defect is influenced by the temperature dependence and a change with the lapse of time (see Japanese Patent Application KOKAI Publication No. 6-38113). A light receiving surface of the electronic camera is shielded by closing an iris immediately after turning on the power. The defect pixel is detected by evaluating the CCD dark output before the use of the camera. And, the defect is compensated based on the information of the detected defect pixel.
However, the defect pixel is occasionally mis-detected by the reverse-incident light from a single lens reflex optical viewfinder. When the reverse-incident light is incident on the imaging device, the reverse-incident light is superimposed on an original photographing signal, and this causes the mis-detection. The dark current is detected in a light-shielded state at the defect detection. Therefore, the influence of light from no-shielded part is large. Moreover, the influence is larger and larger, since it is considered that it is always defect after that when the defect is detected once.
Moreover, even when the technology for acquiring the defect pixel information by using the imaging device output under shielding by closing the iris is used, the extra light is input to the CCD caused by the reverse-incident light from the optical viewfinder and mis-detects the defect in an electronic camera with single lens reflex optical viewfinder occasionally.
Especially, the level of the reverse-incident light from an optical viewfinder is different according to the environment in the camera surroundings. Therefore, since a wrong detection result different from the actual defect level is acquired in every defect detection in the electronic camera which automatically detects the defect pixels, and the detected defect is accumulated.
As the method of reducing the influence of incident light as mentioned above, it is considered that the eyepiece shutter which cuts the reverse-incident light from the viewfinder is provided, but the problem cannot be solved by merely providing the eyepiece shutter. That is, it is necessary to establish a method of preventing, for instance, photographer's operation forgetting including the eyepiece shutter and the operation timing mistake, etc., and a cooperating method of the pixel defect check operation and the eyepiece shutter operation to achieve the certain and good operative defect check operation.